I recently had to deal with the same problem with my 1 year old who so far was such a sweet little nurser. She litterally turned into a monster overnite and would bite constantly. Even went on strike on one side which I tought was fear of my reaction when biting. To make a long story short, it turned out that the little one had thrush! took me a week and sore nipples to figure it out. Once the thrush was under control, everything returned to normal. So from now on I suggest to also look for thrush in mouths of biting babies! Maryelle